1. Field of the Invention
The present invention relates to a portable printing device having a print head capable of printing characters and the like on a print medium, such as a paper sheet, by being scanned across the print medium.
2. Description of the Related Art
There have been known a variety of small portable printing devices having an outer case and a print head housed inside the case. The portable printing devices can be used to print characters and the like at a desired position on print media such as paper sheets. In order to print using such a device, a user scans the case of the portable printing device across the print medium at a desired speed in a printing direction. The portable printing device prints on the print medium using the print head based on an amount of movement of the portable printing device.
For example, there are a number of handy portable printing devices which use a thermal head as the print head. Thermal print devices are convenient because as long as an ink ribbon is provided, printing can be easily performed by manually scanning the case over the printing medium. However, thermal heads rely on transfer of heat to print images so that the thermal head must be extremely close to the printing medium, that is, separated from the print medium only by the ink ribbon, in order to head. Therefore, the thermal print head must be exposed from the outer casing in order to print.
Because the devices are small and compact, the user can easily move them from place to place. However, if the thermal print head is exposed from the case of the portable printing device, the thermal print head can be easily damaged when bumped into other objects. A variety of configurations have been proposed for protecting the thermal head of a thermal type portable printing device when the thermal portable printing device is not being used.
For example, Japanese Laid-Open Patent Publication No. SHO-63-72261 describes a thermal portable printing device including: a fixed link member pivotably fixed at one end to a case; a sliding link member fixed at one end to the free end of the fixed link and at the other end to a print head; and a single rod connected to the linked portion of the link members. A spring urges the linked members to pivot at their linked portion so that the thermal print head is drawn into the case. By pressing the rod against the urging of the spring, the link members straighten out with respect to each other so that the thermal print head is pushed out of the case. By again operating the rod, the print head can be retracted back into the outer case.
Japanese Laid-Open Utility Model Publication No. HEI-1-67052 describes a thermal portable printing device having a swingable frame bolted onto an activation switch. A thermal head is attached to a support frame. A linking mechanism links the swingable frame and the support frame together so that when the activation switch is pushed inward into a non-printing position, the linking mechanism moves the thermal head into a housed position within the outer case and so that when the activation switch is pulled out into a printing position, the linking mechanism lowers the thermal head into a printing position. In this way, the thermal head can be switched between the housed position and the printing position.
Further, Japanese Laid-Open Utility Model Publication No. HEI-2-43059 describes a manual scanning type copy device wherein a printing mechanism including a thermal head is fixed internally in a case near the open lower end portion of the case. A movable member is fitted in the open lower end tip of the case. The movable member can move from a lowered position, wherein its lower end protrudes from the lower end of the case, to a raised position, wherein its lower end is flush with the lower end of the case. The movable member is formed with a hole at a position confronting the thermal head. A lid mechanism is provided for opening and closing the hole in association with raising and lowering movements of the movable member.
With the configuration of Japanese Laid-Open Utility Model Publication No. HEI-2-43059, during non-printing times, that is, when the lower tip portion of the movement member is not placed against a print medium and so protrudes below the lower tip of the case, then the lid closes so that the printing mechanism is housed within the movement member. On the other hand, when the case is pressed against the print medium in order to print characters and the like, the movable member is pushed into the case and, in association with this, the lid slides to the side to open the opening portion so that printing can be performed using the printing mechanism.
There are also a number of handy portable printing devices which use an ink jet head as the print head.
However, ink jet print heads are different from thermal heads, so that ink jet print heads have particular requirements different from those of thermal heads. For example, jet print heads eject ink droplets through tiny nozzles to print images. When ink clinging to the print head surface dries out while the print head is not being used, the dried ink can clog the ink ejection nozzles and interfere with proper ejection of ink droplets.
Stationary ink jet printers, which are normally used in a permanent position on a table or desk top, are provided with a purge mechanism for sucking dried ink from the nozzles to return the ink jet head to a proper printing condition.
Stationary ink jet printers are also provided with a capping mechanism for capping the ink jet print head during non-printing times. The capping mechanism is located at a side position, which is outside the printing region of a carriage on which the ink jet print head is mounted. During non-printing times, the carriage is moved to the position of the capping mechanism and a cap member of the cap mechanism is brought into intimate sealing contact with the head surface of the print head, thereby preventing ink on the head surface drying out.
Japanese Laid-Open Patent Application Publication No. SHO-63-274553 describes a recording device having a case formed with a hole for exposing an ink ejection portion of an ink jet print head. A slidable head cap is provided to slide between the case and the ink jet head in order to prevent ink of the head from drying during non-printing periods, thereby preventing defective ejection of ink.